Creating a warp path filter for get request

Question

I am a Rust beginner and I needed some help with creating path Filters. The stripped down code looks like this:

pub fn requests_filter() -> impl Filter<Extract = impl warp::Reply, Error = warp::Rejection> + Clone {
    let authenticate = warp::get()
            .and(warp::path("/auth")
            .and_then(perform_authentication);

    let get_request = warp::get()
        .and(
            warp::filters::query::raw()
            .or(warp::any().map(|| String::default()))
            .unify(),
        )
        .and(get_header)
        .and_then(process_get_request);

    authenticate.or(get_request)
}

I need to combine the 2 filters so that if I get a auth request(/auth) then it should execute just the first filter and not the second. For all other GET requests it should just execute 2nd path filter. The issue I am having in the above code is the second path filter gets executed when there is some authentication error. I want to it to return and not execute the second path filter. Could you please let me know how to solve this. I looked at routing.rs example but wasnt able to figure this out. Thanks in advance!

Answer 1

The issue I am having in the above code is the second path filter gets executed when there is some authentication error.

Sounds like auth is returning a Rejection on failure.

Sadly that's one part of warp which is very confusing¹: rejections are not for expressing failure, they're the mechanism through which warp triggers "fallbacks" to the next handler in the chain. So by returning a rejection, you tell warp to check whether the next handler might accept the request. This can ultimately yield a failure anyway (if none of the handlers can do anything), but it can also match an run any number of subsequent handlers depending on your routing.

If you want a /auth failure to immediately respond with a failure, you should return a Ok(reply) with whatever failure status and payload you want (e.g. 403 or something), not an Err(failure) which would signal that this handler is unable to handle the request.

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¹: hopefully this changes in 0.4 or 0.5 and filters get a clearer bespoke enum for this rather than override Result.